The isoenzymes of glucose-6-phosphate dehydrogenase (G-6-PD) will be used to study various suspected forerunners of fibrous plaques, and fibrous plaques themselves. Various chemical assays such as determination of alpha-lipoprotein, beta-lipoprotein, fibrinogen and cholesterol will be carried out on the same tissue and comparisons made. The hybrid hare will be used to produce various models of "atherosclerosis". Using the two isoenzyme bands in these hybrids (L. timidus and L. europaeus) we will study the alleged atherosclerotic lesions to see if they are monoclonal.